Project Summary This proposal details a 5-year training plan to aid the continued develop of Dr. Sarah Short, Ph.D. into an independent GI researcher. This research plan will focus on elucidating the role of glutathione peroxidase 1 (GPx1), a ubiquitously expressed selenoenzyme and potent antioxidant, in inflammatory bowel disease (IBD) and colitis-associated dysplasia (CAD). Compelling preliminary data using Gpx1-/- mice indicates that unlike many antioxidants whose loss exacerbates murine colitis, loss of GPx1 confers striking protection from dextran- sodium sulfate (DSS)-induced colitis. GPx1 deficiency also increases survival and stemness in 3D organoids and alters metabolism in tissue culture cells, which may additionally promote regeneration and wound healing. GPx1 expression also modifies immune cell function, as Gpx1-/- bone marrow-derived macrophages have heightened response to ?M2? stimuli and decreased migratory ability. Together, these results suggest that GPx1 augments inflammatory injury through alterations in both epithelial and immune cell function. Based on these finding, the hypothesis of this proposal is that GPx1 is detrimental in inflammatory bowel disease by altering stem cell function, redox homeostasis, and immune responses. Further, inhibiting GPx1 activity may be an effective therapeutic strategy. This hypothesis will be tested in two specific aims to determine how GPx1 contributes to intestinal epithelial cell homeostasis, oxidative stress, colitis, and colitis-associated dysplasia. The first aim will investigate epithelial function, capitalizing on Dr. Short?s over 10 years of experience in epithelial cell biology and barrier function. The second aim will complement epithelial-based studies by determining how GPx1 loss alters immune cell recruitment, differentiation, and function, and identify how these changes modify intestinal injury responses. In addition to being the logical ?next step? experiments in defining GPx1 function, these experiments provide the perfect framework to further Dr. Short?s development in aspects of mucosal immunology which contribute to intestinal diseases, and will include new training in flow cytometry, chemokine analysis, bone marrow transplantation, and the T-cell transfer colitis model. Dr. Short?s career development will be further enhanced by regular discussions with primary mentor, Dr. Christopher Williams, and her mentoring committee consisting of Drs. Keith Wilson, Jeremy Goettel, and Sean Davies. All studies and training will take place at Vanderbilt, and the institution, Department of Medicine, and Gastroenterology Division are highly supportive of Dr. Short?s academic career and fully support her application. Dr. Short?s ultimate goal is to become an independent academic researcher focusing on mechanisms which regulate development and severity of IBD and colitis-associated cancer that can lead to improved therapeutic options for these patients. Interestingly, both specific aims proposed in this application will evaluate GPx1 as a therapeutic target using tiopronin, which is FDA-approved and well-tolerated. Together, these training experiences will ensure Dr. Short is poised to direct a well-rounded independent research program in IBD.